(1) Field of the Invention
The present invention relates to batteries, and more particularly to such batteries as employ bipolar electrodes.
(2) Description of the Prior Art
The employment of bipolar electrodes has been known for some time. Thus, for example, U.S. Pat. No. 627,009 to Paget discloses a storage battery of the lead-acid type which is characterized by the employment of bipolar electrodes. Further more recent interest has been generated in the employment of bipolar electrodes in storage batteries as evidenced by U.S. Pat. Nos. 3,795,543 to Poe, 3,728,158 to Poe et al, 3,817,788 to Eckerbom et al and others. Applicant has noted, however, that the batteries employing bipolar electrodes presently known in the art have not been capable of providing a sufficiently high power density without the employment of relatively thin electrodes of large surface area. The provision of electrodes of large area would require a substantial support structure which would add excess weight to the resulting battery. Further, the relatively small dimension between the cells characteristic of such a battery in the context of the large surface area of the electrodes would result in a battery having a height and width disproportionately large in relation to its length and which would render such a battery spatially unsuitable for certain applications.
The employment of bipolar electrodes in batteries of varying dimension and configuration is likewise illustrated in the prior art. Thus, U.S. Pat. No. 762,715 to Haschke discloses the employment of bipolar electrodes as cell separators in a multiple-cell battery wherein the individual cells are provided with single pole electrodes electrically connected to the respective like pole of the bipolar cell separator element. The Haschke invention which is disclosed as having application to reversible galvanic batteries, and/or primary batteries, is, however, deficient in the cumbersome nature of the construction engendered by the employment of external electrical connections or leads provided between the respective electrodes or plates.
U.S. Pat. No. 2,519,053 to Reinhardt, relating to flat batteries, discloses the construction of a battery comprising a continuous strip of electrodes which are folded on themselves and positioned to be in juxtaposition to each other, wherein the continuous strip comprises a separator for the respective electrodes. Reinhardt, however, does not remedy the deficiency of inadequate power density characteristic of prior art bipolar electrode construction.
U.S. Pat. No. 3,841,914 to Boyle et al relates to a solid state battery comprising a plurality of stacked cylindrical cells, noteworthy in the employment of an electrical connection for each of the positive and negative poles achieved by the employment of an alternating conducting strip which passes between the respective electrodes in alternating, folding fashion. Boyle, however, does not relate to the employment of bipolar electrodes in batteries. In a similar manner to Boyle et al, U.S. Pat. No. 3,108,908 to Krebs relates to a hermetically sealed storage battery which employs oppositely charged electrodes in alternating disposition with oppositely directed electrical connectors providing electrical connection between electrodes of like charge. Also, the electrodes are separated by a continuous material which weaves between the respective electrodes. Krebs, however, also fails to disclose the employment of bipolar electrodes in batteries.
In addition to the disclosures discussed above, other patents are known that are believed relevant to the state of the art. Thus, Canadian Pat. No. 636,212 to Nelson discloses that a plurality of bipolar electrodes may be fabricated in continuous strip-like fashion and then alternately folded or stacked. British Pat. No. 225,407 to Weissman illustrates a battery employing a continuous, folding negative electrode which alternates to contain a plurality of negative electrode units. U.S. Pat. No. 3,723,181 to Oakley discloses the preparation of individual bipolar electrode units by a method comprising the deposition of the electrically active material on both sides of a continuous, non-conductive strip, whereby deposition of the specific electrode material is placed over an initial deposition of conductive material connecting the respective sides of the strip. Likewise, U.S. Pat. No. 3,784,410 to Bergum et al discloses the production of bipolar electrodes by deposition of the active material upon a continuous metal strip having two non-reactive metal sides. All of the foregoing patents relate to aspects of battery technology, however none deal with the problem of efficiently increasing the power density obtainable from bipolar electrodes in battery construction.